MAYBE try apple juice, prune juice, or any other constipation relief method around mid day to encourage an earlier bowel movement. I know the issue isn't constipation but maybe it could help. Consult with doctor first if any hesitation or concerns or any health concerns
It could have to do with the time of his feedings. You could try feeding him earlier before bed time? I’m sorry, that’s all I’ve got. My little one has trouble pooping so we have to give her apple juice to help it along.